On 2/11/21 2:12 PM, Kenneth wrote:
> I've been away from the newsgroups for awhile-- busy running lots of radiosity
> tests (and fixing computer problems). Along the way, I noticed something about
> the renders that has nothing to do with radiosity, but with antialiasing.
> 
...
> 

A little of what you are seeing I believe is related to the AA 
discussions in the threads (exploration you more or less got me into :-)).

http://news.povray.org/povray.general/thread/%3C5f9c4a2f%241%40news.povray.org%3E/

and

http://news.povray.org/povray.beta-test.binaries/thread/%3C5f9d5730%241%40news.povray.org%3E/


In other words, more flexible AA helps - a little.

---

To support the high dynamic range outputs not sure what can be done 
except some kind of post processing as Cousin Ricky suggested. At the 
time AA is done it knows about the color channel values and nothing 
more. With color values >>1 there simply is a massive difference between 
adjacent pixels. If you have say emission 10 even with some sort of 
bloom / blend, you'll need consume 10 or more pixels around the ultra 
bright regions to get into a range were you'd get AA on the '<=1.0' edge.

I had the thought this morning one way to post process using big jitter 
aa would be to output to hdr or exr, read the image back in dividing by 
the largest 'emission' value. Output, re-scale up the intensity, but 
clamping channels at 1.0 (or what ever). Probably would need to handle 
each color channel separately.

Attached is an image where in the top row you see the current output to 
png with clamping to 1.0 for the two right spheres at emission 5 and 9.9.

When I write to exr or hdr I was expecting linear encoded values, but 
this is not what I see...

To get what I wanted in the bottom row reading the exr/hdr images back 
into POV-Ray, instead of dividing by 9.9 as I believe is correct if 
everything linear, I had to divide by 174.125. A value which looks to 
have been gamma corrected.

Gimp agrees the written exr/hdr values have been gamma corrected. I've 
not looked into other exr/hdr dump value utilities

I believe exr and hdr input and output are supposed to be linear. Am I 
missing something? I don't have very much experience using exr, hdr. 
Except to use ones others have generated for environmental lighting and 
the read path seems OK.

I tried things like File_Gamma and gamma controls, but as the docs say 
these appeared to be ignored for exr/hdr files.

Bill P.

Aside: As a speed up for parametrics I'd played with writing the three 
x,y,z channels to image files. Using function based on those image files 
in scene instead, but the surfaces were very rough. I attributed it to 
not enough bit depth, but if the exr files were not linear, that could 
be why the method didn't work very well.

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